Color electrophotographic process and apparatus

Abstract

A process and apparatus are provided for printing particles of a color toner that is selectively colored and can demonstrate or reflect color based upon exposure to light of known wavelength, intensity, and duration. The color toner is sensitive to a plurality of wavelengths to provide a desired color. The apparatus performs three basic functions: (1) applies the toner to a print medium, using an electrophotographic process, requiring the toner to be chargeable; (2) selectively applies light to the toner, the light being of known wavelength, intensity, and duration, to convert the toner particles to the desired color(s); and (3) bonds or attaches the toner to the print medium. Since the color toner includes all necessary colors that are selectively activated, only one color toner and thus only application of one color toner is required. The process (1) increases the robustness of color image processing and mechanically simplifies the process of application and (2) results in high quality, time-enduring images.

What is claimed is:  
     
       1. A process for printing particles of a color toner that is selectively colored and can demonstrate or reflect color based upon exposure to light of known wavelength, intensity, and duration, said process comprising: 
       (a) providing a print medium for transport through a printing device;  
       (b) developing an image by directing a light source to shine energy to finite areas on a surface of a rotating electrophotographic element, thereby charging said finite areas on said surface of said electrophotographic element;  
       (c) passing said surface of said rotating electrophotographic element through a toner source to attract said toner particles to said laser-charged finite areas on said surface of said electrophotographic element, said toner particles being initially translucent and containing a combination of at least one light-sensitive oxidizing agent, at least one developing agent, at least one color coupling agent, and, optionally, at least one fixing agent;  
       (d) providing a charge to a transfer roller that forms a nip with said electrophotographic element while said print medium is passed through said nip, thereby transferring said toner particles to said print medium by attracting said toner particles away from said electrophotographic element, said toner particles remaining on said print medium as said print medium leaves said nip;  
       (e) selectively exposing said toner particles by light of known wavelength, intensity, and duration;  
       (f) initiating (1) excitation reactions, (2) developer reactions, and (3) color coupling reactions, as appropriate, in said toner particles, thereby providing a selected color dependent upon said wavelength;  
       (g) fixing said toner particles; and  
       (h) bonding said toner particles to said print medium.  
     
     
       2. The process of  claim 1  wherein said color toner comprises particles of one type, which provide a color dependent on exposure to a specific wavelength. 
     
     
       3. The process of  claim 2  wherein said color toner provides additive or subtractive chromophores, or variants of such colors, depending upon said specific wavelength. 
     
     
       4. The process of  claim 3  wherein said chromophores comprise a set of cyan, yellow, and magenta colors. 
     
     
       5. The process of  claim 1  wherein said at least one light-sensitive oxidizing agent comprises color-sensitized silver halide crystals. 
     
     
       6. The process of  claim 1  wherein said light source comprises a laser. 
     
     
       7. The process of  claim 1  wherein said light of known wavelength, intensity, and duration is provided by at least one laser, at least one cathode ray tube, at least one light emitting diode, or filtered white light. 
     
     
       8. The process of  claim 1  wherein said fixing is accomplished by bathing said at least one light-sensitive oxidizing agent with electrons via an electronic source of current or charge. 
     
     
       9. The process of  claim 1  wherein said fixing is accomplished by including at least one fixing agent in said toner particles and rupturing or mixing said at least one fixing agent with pressure. 
     
     
       10. The process of  claim 1  wherein steps (g) and (h) are carried out in a single step. 
     
     
       11. Apparatus for printing particles of a color toner is selectively colored and can demonstrate or reflect color based upon exposure to light of known wavelength, intensity, and duration, said apparatus comprising: 
       (a) a medium transport for transporting print media through said apparatus on which said toner particles are printed;  
       (b) a rotatable electrophotographic element;  
       (c) a light source for shining radiation on finite areas of said electrophotographic element, thereby charging said finite areas on said element;  
       (d) a source containing a quantity of said toner particles, which are attracted to said laser-charged finite areas on a surface of said electrophotographic element as said surface of said rotating element is passed through said toner source, said toner particles being initially translucent and containing a combination of at least one light-sensitive oxidizing agent, at least one developing agent, at least one color coupling agent, and, optionally, at least one fixing agent;  
       (e) a transfer roller urged against said electrophotographic element with sufficient pressure to form a nip through which said print medium is transported, said transfer roller being charged to attract said toner particles away from said electrophotographic element and onto said print medium;  
       (f) at least one light source for exposing said toner particles to light of known wavelength, intensity, and duration to initiate (1) excitation reactions, (2) developer reactions, and (3) color coupler reactions, as appropriate in said toner particles, thereby providing a selected color dependent upon said wavelength;  
       (g) a fixing mechanism for fixing said toner particles; and  
       (h) a fuser for bonding said toner particles to said print medium.  
     
     
       12. The apparatus of  claim 11  wherein said color toner comprises particles of one type, which provide a color dependent on exposure to a specific wavelength. 
     
     
       13. The apparatus of  claim 12  wherein said color toner provides additive or subtractive chromophores, or variants of such colors, depending upon said specific wavelength. 
     
     
       14. The apparatus of  claim 13  wherein said chromophores comprise a set of cyan, yellow, and magenta colors. 
     
     
       15. The apparatus of  claim 11  wherein said at least one light-sensitive oxidizing agent comprises color-sensitized silver halide crystals. 
     
     
       16. The apparatus of  claim 11  wherein said light source comprises a laser. 
     
     
       17. The apparatus of  claim 11  wherein said light of known wavelength, intensity, and duration is provided by at least one laser, at least one cathode ray tube, at least one light emitting diode, or filtered white light. 
     
     
       18. The apparatus of  claim 11  wherein said fixing mechanism comprises an electronic source for bathing said at least one light-sensitive oxidizing agent with electrons of current or charge. 
     
     
       19. The apparatus of  claim 11  wherein said fixing mechanism comprises at least one fixing agent included in said toner particles and a mechanism for rupturing or mixing said at least one fixing agent with pressure. 
     
     
       20. The apparatus of  claim 11  wherein elements (g) and (h) comprise a single element for said fixing and said bonding.